I'd say you def wanna stick with a 245 at least. A 235 is too skinny IMHO unless you want a very slight stretch or something. A 245/40R18 would be a good option or a 255/35R18 would give you a nice squared looked.

I have 245/40 tires on my 17x9 +42 wheels. My fenders were rolled and pulled by IAG Performance and I have plenty of clearance and zero rubbing issues at stock height, so I think you'll probably be ok with that setup. Are you planning to do the fender work yourself?

There's a guy in my area that works at a body shop and has a fender roller. so I'm gonna roll all 4 of my fenders and I guess go with 245/40/18 on mine and hope it doesn't rub since mine is lowered on gf210

8.5" +42 with 245 tire? You'll rub on stock fenders. You won't rub if nobody's in the back and you drive on bump free roads but if the suspension compresses, the back fenders will eat your tire some. Roll would probably suffice.

you want shorter than 25", not taller. It'll help your gearing and also your clearance.

235/35R18 on 18x8.5" +42 is close. I'm not sure if it would require rear fender rolling or not. Probably matters on how much you care about the very occasional scrape when you hit a big bump, if you have lowering springs, and how often you put people in the back seat. Certainly with a rear fender roll you'd have zero issues... other than some serious steering response losses from +42 offset.

I've owned the car for about 6 months and I haven't had 1 person in the back seat haha. The only prob with a 235/35/18 is I don't like the small sidewall. Already have a time set up to have all 4 fenders rolled. The 235/40/18 seemed like the perfect Candidate for tire size untill you mentioned about gearing

If you want 40 sidewall and 235 wide but don't want to mess up your gearing, there's an easy solution: BUY 17" WHEELS!

Your stock size is 215/45R17. It's substantially less than 25". 235/40R18 is substantially more than 25". I would recommend a stock gearing or tighter. The 5-speed in your car is fairly tall. Smaller tires will help with low end pickup, reduce lag, and increase overall acceleration. It's an AWD car with fairly moderate HP, you don't need to worry about spinning tires. You also don't need to worry about cutting top speed as 5th goes on your stock gearing to well over the aerodynamic limit of your car (160+ if I recall correctly). In other words, lowering your gearing is a no brainer for any analysis beyond "the look". Now, I wouldn't drop below 24" or so, that's going to be too far out of factory spec and will cause other issues (changes in suspension geometry, etc). But certainly you want to err on the side of shorter tires than purposely getting one a full inch taller than your stock tire.

Also, on a personal standpoint, I think people who have massive diameter wheels which show off tiny little brakes underneath them rather silly. The look of the brakes actually filling the wheel diameter (hence a functional purpose for the wheel diameter in the first place) really make a car look more sporty to me. Seriously, you don't see anything weird looking at the rear of a WRX with 18" wheels on that are a full 3" from the brake caliber? The 06 WRX has nice front brakes which require special 15" wheels to clear. 16" is easier and still fills out the wheel. 17" is at least reasonable looking. 18" makes even your front brakes (which are bigger than 02-05 and 08+ wrx to be fair) look tiny.